From 3aa7857fe1d7ac7f600f5b7e1530396fb06822bf Mon Sep 17 00:00:00 2001 From: Neil Spring Date: Wed, 25 Aug 2021 14:01:17 -0700 Subject: [PATCH] tcp: enable mid stream window clamp The TCP_WINDOW_CLAMP socket option is defined in tcp(7) to "Bound the size of the advertised window to this value." Window clamping is distributed across two variables, window_clamp ("Maximal window to advertise" in tcp.h) and rcv_ssthresh ("Current window clamp"). This patch updates the function where the window clamp is set to also reduce the current window clamp, rcv_sshthresh, if needed. With this, setting the TCP_WINDOW_CLAMP option has the documented effect of limiting the window. Signed-off-by: Neil Spring Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20210825210117.1668371-1-ntspring@fb.com Signed-off-by: Jakub Kicinski --- net/ipv4/tcp.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index f931def6302e..e8b48df73c85 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3338,6 +3338,7 @@ int tcp_set_window_clamp(struct sock *sk, int val) } else { tp->window_clamp = val < SOCK_MIN_RCVBUF / 2 ? SOCK_MIN_RCVBUF / 2 : val; + tp->rcv_ssthresh = min(tp->rcv_wnd, tp->window_clamp); } return 0; } -- 2.25.1